Parsing Utilities

Overview

Parsing utilities are a set of functions that helps generate parsing spec for tf$parse_example to be used with estimators. If users keep data in tf$Example format, they need to call
tf$parse_example with a proper feature spec. There are two main things that
these utility functions help:

Users need to combine parsing spec of features with labels and weights (if any) since they are all parsed from same tf$Example instance. The utility functions combine these specs.

It is difficult to map expected label by a estimator such as dnn_classifier
to corresponding tf$parse_example spec. The utility functions encode it by getting
related information from users (key, dtype).